One of the tool most often associated with training related to striking an opponent is the punching (or heavy) bag. A punching bag is usually cylindrical, and filled with various materials of corresponding hardness. While a punching bag is great for some punches, it is not designed for someone to practice an upper cut (a punch that travels upwards typically to an opponent's chin or solar plexus). Because the glancing nature of the upper cut on the punching bag, it would cause a significant torque on the wrist of person doing the punching and could lead to significant injury. Torque is the enemy to safety during training.
In order to practice punches such as an uppercut, punching mitts worn on a trainers hands are typically employed. In the case of a punching mitt, the individual practicing the punch is supposed to punch the mitt head on and the person wearing the mitt it is supposed to resist the force of the punch using their hands and arms.
However, as good as the punching mitt is, a single mitt can only be used to practice one punch at a time because it is difficult for an individual absorbing a blow with their body to accurately move to the next position in order to receive the next blow in a combination of punches.
Delivering a blow is not the only time it can be dangerous and lead to injury. Receiving a blow typically for new fighters is a significant source of injury, which is why beginning fighters all wear headgear.
Learning how to “slip” a punch (moving your body out of the way of an opponent's punch so that the opponent's fist just misses you) is an essential skill to learn. But practicing not being punched will inevitably lead to a few occasions when punches are accidentally received, particularly as practice is sped up. The problem is that the trainer is either throwing a punch in the air to the side of the trainee's face or at the trainee's face and the trainee is supposed to move. In the first case the trainer not having a specific target is likely to strike the trainee from time to time or at the very least greatly vary the location of their punches. In the second case, the trainee is highly likely to be struck; however, even when they aren't struck, the trainee has no feedback as to how successful they were at slipping the punch other than whether or not they were hit or not. There is no feedback about the degree of success (e.g. was slipped by inches or fractions of an inch). Note: in order to conserve their energy and also to be able to deliver a counter punch, the fighter ideally wants to slip a punch by the smallest distance possible.
Therefore, there continues to be a need for improved safety and feedback when individuals are practicing striking an opponent.